@article{DAN_1967_173_6_a8,
     author = {Yu. V. Matiyasevich},
     title = {Simple examples of unsolvable associative calculi},
     journal = {Doklady Akademii Nauk},
     pages = {1264--1266},
     publisher = {mathdoc},
     volume = {173},
     number = {6},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1967_173_6_a8/}
}